The Imaging Core has been introduced, thanks to a supplementary grant awarded by NCI in 1998. The idea of including imaging expertise to this Program rose through the scientific interaction of Program investigators with Dr. Blasberg and Dr. Tjuvajev; some of which have already generated joint publications The main objective of the core will be to support eh individual projects with respect to monitoring the distribution of genetically engineered cells in vivo, in pre-clinical and eventually in clinical studies. For instance, the homing of genetically altered T cells to tumor sites can be monitored by quantitative, non-invasive imaging using positron emission tomography (PET) or gamma camera imaging techniques. The aims of the core will be pursued be building on published studies, which have demonstrated the ability to selectively image HSV1- tk transgene expression. The rationale for the proposed imaging experiments is based on preliminary data showing that T cells expressing HSV1-tk can be sequentially imaged and monitored as they migrate through the body to the target (tumor) site. The potential of the Imaging Core is based on the scientific expertise of its leader Dr. Ronald Blasberg and of the other investigators, who have strong rack records in the area of in vitro and in vivo imaging. The Imaging Core has access to highly sophisticated instruments, which taken together, constitute a unique set of imaging apparatus in terms of achieving a resolution power suitable for the analysis of relatively small numbers of cells in small animals. The Imaging Core will facilitate Project 1, Project 2 and Project 4 to image and monitor targeting of genetically altered T cells to tumors. With Project 3, the Imaging Core will image and monitor in vivo homing of hematopoietic cells to bone marrow. If these imaging goals can be achieved in experimental animals, it is expected that they will be directly transferable to human studies using currently available clinical imaging facilities at MSKCC, including positron emission tomography (PET) and magnetic resonance imaging (MRI).